/*
 * Copyright 2016, Blender Foundation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * Contributor(s): Blender Institute
 *
 */

/** \file eevee_occlusion.c
 *  \ingroup draw_engine
 *
 * Implementation of the screen space Ground Truth Ambient Occlusion.
 */

#include "DRW_render.h"

#include "BLI_string_utils.h"

#include "DNA_anim_types.h"

#include "DEG_depsgraph_query.h"

#include "BKE_global.h" /* for G.debug_value */

#include "eevee_private.h"

#include "GPU_extensions.h"
#include "GPU_state.h"

static struct {
	/* Ground Truth Ambient Occlusion */
	struct GPUShader *gtao_sh;
	struct GPUShader *gtao_layer_sh;
	struct GPUShader *gtao_debug_sh;
	struct GPUTexture *src_depth;
} e_data = {NULL}; /* Engine data */

extern char datatoc_ambient_occlusion_lib_glsl[];
extern char datatoc_common_view_lib_glsl[];
extern char datatoc_common_uniforms_lib_glsl[];
extern char datatoc_bsdf_common_lib_glsl[];
extern char datatoc_effect_gtao_frag_glsl[];

static void eevee_create_shader_occlusion(void)
{
	char *frag_str = BLI_string_joinN(
	        datatoc_common_view_lib_glsl,
	        datatoc_common_uniforms_lib_glsl,
	        datatoc_bsdf_common_lib_glsl,
	        datatoc_ambient_occlusion_lib_glsl,
	        datatoc_effect_gtao_frag_glsl);

	e_data.gtao_sh = DRW_shader_create_fullscreen(frag_str, NULL);
	e_data.gtao_layer_sh = DRW_shader_create_fullscreen(frag_str, "#define LAYERED_DEPTH\n");
	e_data.gtao_debug_sh = DRW_shader_create_fullscreen(frag_str, "#define DEBUG_AO\n");

	MEM_freeN(frag_str);
}

int EEVEE_occlusion_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
{
	EEVEE_CommonUniformBuffer *common_data = &sldata->common_data;
	EEVEE_FramebufferList *fbl = vedata->fbl;
	EEVEE_StorageList *stl = vedata->stl;
	EEVEE_EffectsInfo *effects = stl->effects;

	const DRWContextState *draw_ctx = DRW_context_state_get();
	const Scene *scene_eval = DEG_get_evaluated_scene(draw_ctx->depsgraph);

	if (scene_eval->eevee.flag & SCE_EEVEE_GTAO_ENABLED) {
		const float *viewport_size = DRW_viewport_size_get();
		const int fs_size[2] = {(int)viewport_size[0], (int)viewport_size[1]};

		/* Shaders */
		if (!e_data.gtao_sh) {
			eevee_create_shader_occlusion();
		}

		common_data->ao_dist = scene_eval->eevee.gtao_distance;
		common_data->ao_factor = scene_eval->eevee.gtao_factor;
		common_data->ao_quality = 1.0f - scene_eval->eevee.gtao_quality;

		common_data->ao_settings = 1.0f; /* USE_AO */
		if (scene_eval->eevee.flag & SCE_EEVEE_GTAO_BENT_NORMALS) {
			common_data->ao_settings += 2.0f; /* USE_BENT_NORMAL */
		}
		if (scene_eval->eevee.flag & SCE_EEVEE_GTAO_BOUNCE) {
			common_data->ao_settings += 4.0f; /* USE_DENOISE */
		}

		common_data->ao_bounce_fac = (scene_eval->eevee.flag & SCE_EEVEE_GTAO_BOUNCE) ? 1.0f : 0.0f;

		effects->gtao_horizons = DRW_texture_pool_query_2D(fs_size[0], fs_size[1], GPU_RGBA8,
		                                                   &draw_engine_eevee_type);
		GPU_framebuffer_ensure_config(&fbl->gtao_fb, {
			GPU_ATTACHMENT_NONE,
			GPU_ATTACHMENT_TEXTURE(effects->gtao_horizons)
		});

		if (G.debug_value == 6) {
			effects->gtao_horizons_debug = DRW_texture_pool_query_2D(fs_size[0], fs_size[1], GPU_RGBA8,
			                                                         &draw_engine_eevee_type);
			GPU_framebuffer_ensure_config(&fbl->gtao_debug_fb, {
				GPU_ATTACHMENT_NONE,
				GPU_ATTACHMENT_TEXTURE(effects->gtao_horizons_debug)
			});
		}
		else {
			effects->gtao_horizons_debug = NULL;
		}

		return EFFECT_GTAO | EFFECT_NORMAL_BUFFER;
	}

	/* Cleanup */
	effects->gtao_horizons = NULL;
	GPU_FRAMEBUFFER_FREE_SAFE(fbl->gtao_fb);
	common_data->ao_settings = 0.0f;

	return 0;
}

void EEVEE_occlusion_output_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
{
	EEVEE_FramebufferList *fbl = vedata->fbl;
	EEVEE_TextureList *txl = vedata->txl;
	EEVEE_StorageList *stl = vedata->stl;
	EEVEE_PassList *psl = vedata->psl;
	EEVEE_EffectsInfo *effects = stl->effects;

	const DRWContextState *draw_ctx = DRW_context_state_get();
	const Scene *scene_eval = DEG_get_evaluated_scene(draw_ctx->depsgraph);

	if (scene_eval->eevee.flag & SCE_EEVEE_GTAO_ENABLED) {
		DefaultTextureList *dtxl = DRW_viewport_texture_list_get();
		float clear[4] = {0.0f, 0.0f, 0.0f, 0.0f};

		DRW_texture_ensure_fullscreen_2D(&txl->ao_accum, GPU_R32F, 0); /* Should be enough precision for many samples. */

		GPU_framebuffer_ensure_config(&fbl->ao_accum_fb, {
			GPU_ATTACHMENT_NONE,
			GPU_ATTACHMENT_TEXTURE(txl->ao_accum)
		});

		/* Clear texture. */
		GPU_framebuffer_bind(fbl->ao_accum_fb);
		GPU_framebuffer_clear_color(fbl->ao_accum_fb, clear);

		/* Accumulation pass */
		DRWState state = DRW_STATE_WRITE_COLOR | DRW_STATE_ADDITIVE;
		psl->ao_accum_ps = DRW_pass_create("AO Accum", state);
		DRWShadingGroup *grp = DRW_shgroup_create(e_data.gtao_debug_sh, psl->ao_accum_ps);
		DRW_shgroup_uniform_texture(grp, "utilTex", EEVEE_materials_get_util_tex());
		DRW_shgroup_uniform_texture_ref(grp, "maxzBuffer", &txl->maxzbuffer);
		DRW_shgroup_uniform_texture_ref(grp, "depthBuffer", &dtxl->depth);
		DRW_shgroup_uniform_texture_ref(grp, "normalBuffer", &effects->ssr_normal_input);
		DRW_shgroup_uniform_texture_ref(grp, "horizonBuffer", &effects->gtao_horizons);
		DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
		DRW_shgroup_call_add(grp, DRW_cache_fullscreen_quad_get(), NULL);
	}
	else {
		/* Cleanup to release memory */
		DRW_TEXTURE_FREE_SAFE(txl->ao_accum);
		GPU_FRAMEBUFFER_FREE_SAFE(fbl->ao_accum_fb);
	}
}

void EEVEE_occlusion_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
{
	EEVEE_PassList *psl = vedata->psl;
	EEVEE_StorageList *stl = vedata->stl;
	EEVEE_TextureList *txl = vedata->txl;
	EEVEE_EffectsInfo *effects = stl->effects;
	DefaultTextureList *dtxl = DRW_viewport_texture_list_get();

	struct GPUBatch *quad = DRW_cache_fullscreen_quad_get();

	if ((effects->enabled_effects & EFFECT_GTAO) != 0) {
		/**  Occlusion algorithm overview
		 *
		 *  We separate the computation into 2 steps.
		 *
		 * - First we scan the neighborhood pixels to find the maximum horizon angle.
		 *   We save this angle in a RG8 array texture.
		 *
		 * - Then we use this angle to compute occlusion with the shading normal at
		 *   the shading stage. This let us do correct shadowing for each diffuse / specular
		 *   lobe present in the shader using the correct normal.
		 **/
		psl->ao_horizon_search = DRW_pass_create("GTAO Horizon Search", DRW_STATE_WRITE_COLOR);
		DRWShadingGroup *grp = DRW_shgroup_create(e_data.gtao_sh, psl->ao_horizon_search);
		DRW_shgroup_uniform_texture(grp, "utilTex", EEVEE_materials_get_util_tex());
		DRW_shgroup_uniform_texture_ref(grp, "maxzBuffer", &txl->maxzbuffer);
		DRW_shgroup_uniform_texture_ref(grp, "depthBuffer", &effects->ao_src_depth);
		DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
		DRW_shgroup_call_add(grp, quad, NULL);

		psl->ao_horizon_search_layer = DRW_pass_create("GTAO Horizon Search Layer", DRW_STATE_WRITE_COLOR);
		grp = DRW_shgroup_create(e_data.gtao_layer_sh, psl->ao_horizon_search_layer);
		DRW_shgroup_uniform_texture(grp, "utilTex", EEVEE_materials_get_util_tex());
		DRW_shgroup_uniform_texture_ref(grp, "maxzBuffer", &txl->maxzbuffer);
		DRW_shgroup_uniform_texture_ref(grp, "depthBufferLayered", &effects->ao_src_depth);
		DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
		DRW_shgroup_uniform_int(grp, "layer", &stl->effects->ao_depth_layer, 1);
		DRW_shgroup_call_add(grp, quad, NULL);

		if (G.debug_value == 6) {
			psl->ao_horizon_debug = DRW_pass_create("GTAO Horizon Debug", DRW_STATE_WRITE_COLOR);
			grp = DRW_shgroup_create(e_data.gtao_debug_sh, psl->ao_horizon_debug);
			DRW_shgroup_uniform_texture(grp, "utilTex", EEVEE_materials_get_util_tex());
			DRW_shgroup_uniform_texture_ref(grp, "maxzBuffer", &txl->maxzbuffer);
			DRW_shgroup_uniform_texture_ref(grp, "depthBuffer", &dtxl->depth);
			DRW_shgroup_uniform_texture_ref(grp, "normalBuffer", &effects->ssr_normal_input);
			DRW_shgroup_uniform_texture_ref(grp, "horizonBuffer", &effects->gtao_horizons);
			DRW_shgroup_uniform_block(grp, "common_block", sldata->common_ubo);
			DRW_shgroup_call_add(grp, quad, NULL);
		}
	}
}

void EEVEE_occlusion_compute(
        EEVEE_ViewLayerData *UNUSED(sldata), EEVEE_Data *vedata, struct GPUTexture *depth_src, int layer)
{
	EEVEE_PassList *psl = vedata->psl;
	EEVEE_FramebufferList *fbl = vedata->fbl;
	EEVEE_StorageList *stl = vedata->stl;
	EEVEE_EffectsInfo *effects = stl->effects;

	if ((effects->enabled_effects & EFFECT_GTAO) != 0) {
		DRW_stats_group_start("GTAO Horizon Scan");
		effects->ao_src_depth = depth_src;
		effects->ao_depth_layer = layer;

		GPU_framebuffer_bind(fbl->gtao_fb);

		if (layer >= 0) {
			DRW_draw_pass(psl->ao_horizon_search_layer);
		}
		else {
			DRW_draw_pass(psl->ao_horizon_search);
		}

		if (GPU_mip_render_workaround() ||
		    GPU_type_matches(GPU_DEVICE_INTEL_UHD, GPU_OS_WIN, GPU_DRIVER_ANY))
		{
			/* Fix dot corruption on intel HD5XX/HD6XX series. */
			GPU_flush();
		}

		/* Restore */
		GPU_framebuffer_bind(fbl->main_fb);

		DRW_stats_group_end();
	}
}

void EEVEE_occlusion_draw_debug(EEVEE_ViewLayerData *UNUSED(sldata), EEVEE_Data *vedata)
{
	EEVEE_PassList *psl = vedata->psl;
	EEVEE_FramebufferList *fbl = vedata->fbl;
	EEVEE_StorageList *stl = vedata->stl;
	EEVEE_EffectsInfo *effects = stl->effects;

	if (((effects->enabled_effects & EFFECT_GTAO) != 0) && (G.debug_value == 6)) {
		DRW_stats_group_start("GTAO Debug");

		GPU_framebuffer_bind(fbl->gtao_debug_fb);
		DRW_draw_pass(psl->ao_horizon_debug);

		/* Restore */
		GPU_framebuffer_bind(fbl->main_fb);

		DRW_stats_group_end();
	}
}

void EEVEE_occlusion_output_accumulate(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
{
	EEVEE_FramebufferList *fbl = vedata->fbl;
	EEVEE_PassList *psl = vedata->psl;

	if (fbl->ao_accum_fb != NULL) {
		DefaultTextureList *dtxl = DRW_viewport_texture_list_get();

		/* Update the min_max/horizon buffers so the refracion materials appear in it. */
		EEVEE_create_minmax_buffer(vedata, dtxl->depth, -1);
		EEVEE_occlusion_compute(sldata, vedata, dtxl->depth, -1);

		GPU_framebuffer_bind(fbl->ao_accum_fb);
		DRW_draw_pass(psl->ao_accum_ps);

		/* Restore */
		GPU_framebuffer_bind(fbl->main_fb);
	}
}

void EEVEE_occlusion_free(void)
{
	DRW_SHADER_FREE_SAFE(e_data.gtao_sh);
	DRW_SHADER_FREE_SAFE(e_data.gtao_layer_sh);
	DRW_SHADER_FREE_SAFE(e_data.gtao_debug_sh);
}
